Field of Invention
The following description relates to a digital x-ray detector wherein a PIN diode may be prevented from being damaged in a process of repairing a bad pixel using laser, and a method for repairing the bad pixel thereof.
Description of Related Art
Methods for detecting an x-ray include a method of directly detecting an x-ray and a method of indirectly detecting an x-ray by converting the x-ray into a visible ray and then detecting the x-ray using the visible ray.
An x-ray detector using the aforementioned indirect method consists of an element to convert an x-ray into a visible ray, an element to convert the visible ray into an electronic signal, and an element to convert the electronic signal into an image signal. In other words, the x-ray detector using the indirect method is an apparatus configured to convert an emitted x-ray eventually into an image signal.
Hereinafter, a conventional indirect type digital x-ray detector (hereinafter referred to as a ‘digital x-ray detector’) will be explained with reference to the drawings attached.
FIG. 1 is a schematic cross-sectional view illustrating a conventional digital x-ray detector; FIG. 2 is a schematic top view of the conventional digital x-ray detector; and FIG. 3 is an enlarged view of major parts of FIG. 2.
As illustrated in FIGS. 1 to 3, the conventional digital x-ray detector includes a substrate 10, a gate line 20 and a data line 30 disposed on the substrate 10 such that the gale line and the data line intersect each other, a thin film transistor 40 formed on an intersecting region of the gate line 20 and the data line 30, a PIN diode 50 disposed on a pixel domain, a bias line 60 disposed above the PIN diode 50 such that it is parallel to the data line 30, and a scintillator 70.
The thin film transistor 40 is formed on the substrate 40, and includes a gate electrode 21, an active layer 41, a source electrode 42 and a drain electrode 43.
The PIN diode 50 includes a lower electrode 51 that is electrically connected to the thin film transistor 20; a layer 52 that includes a P (Positive) type semiconductor layer, an I (Intrinsic) type semiconductor layer, and an N (Negative) type semiconductor layer successively deposited on the lower electrode 51; and an ITO upper electrode 53.
The scintillator 70 is formed on the PIN diode 50 and serves to convert an x-ray into a visible ray.
Hereinafter, operations of such a conventional digital x-ray detector will be explained.
When an x-ray is emitted to the scintillator 70, the x-ray is converted into a visible ray in the scintillator 70, and then the visible ray is transmitted to the PIN diode 50. The visible ray transmitted to the PIN diode 50 is converted into an electronic signal in the PIN diode 50, and the converted electronic signal is converted into an image signal through the thin film transistor, and is then displayed.
Generally, in a digital x-ray detector, from a minimum of tens of thousands up to a maximum of tens of millions of pixels are formed with different sizes and resolutions, and thus it would take too much failure cost to manufacture an array substrate such that all those tens of thousands or tens of millions of pixels operate normally. Therefore, array substrates of fair quality if not the best quality are being manufactured as long as they satisfy minimum requirements.
However, due to the recent increasing demand from customers to improve the display quality, efforts are being made for processes that could repair bad pixels.
Specifically, after an x-ray is converted into a visible ray in a scintillator, the visible ray is converted into an electronic signal in a PIN diode, and then the converted electronic signal is displayed as an image signal after going through a thin film transistor. Herein, should there be a bad pixel that retains its state of being bright spot, the bright spot will be clearly recognizable. Accordingly, efforts are being made to provide a repair process that could keep the bad pixel in a state of a dark spot.
It is generally easy for a human eye to recognize a white spot on a black background than a black spot on a white background, and thus to reduce the recognizability of a bad pixel, it is general to darkening or blackening the bad pixel.
Therefore, when manufacturing an array substrate for a digital x-ray detector, a bright bad pixel is repaired to appear darker while leaving a dark bad pixel as it is, thereby reducing the recognizability of the bad pixels.
In an array substrate for a conventional digital x-ray detector, darkening a bad pixel is performed by cutting a drain electrode 43 (“A” part shown in dotted lines in FIG. 3) of the thin film transistor 40 by emitting a laser.
However, in the pattern design of an array substrate of such a conventional digital x-ray detector, the distance between the drain electrode 43 and a PIN diode is too close to perform the repair process, and thus the PIN diode 50 may be damaged by the laser in the process of cutting the drain electrode 43 using the laser, and when the PIN diode 50 is damaged, the unstable state of a current may affect a PIN diode of a neighboring pixel as well, causing the PIN diode 50 of the neighboring pixel to malfunction. Thus, performing the process of repairing a bad pixel is not easy.